Mass Timber in North America
Learning Objectives - After this course, you should be able to:
- Examine the trend toward mass timber buildings in the context of carbon footprint, construction efficiency, fire and life safety, occupant well-being, and other potential advantages.
- Identify a range of mass timber products available to North American building designers.
- Discuss research and resources related to the structural performance and fire/life safety of mass timber products.
- Based on examples of mass timber buildings either built or under construction, describe how all-wood and hybrid systems are expanding the options for wood design.
It’s been a while since a major category of building materials inspired the kind of widespread enthusiasm currently being shown for mass timber. Around the world, designers are leveraging the strength, stability, and design flexibility of products such as cross-laminated timber (CLT) to push beyond wood’s perceived boundaries, achieving building heights and spans that would have once required concrete, steel, or masonry for structural support.
Photo courtesy of LEVER Architecture
Location: Portland, Oregon
Architect: LEVER Architecture
Structural Engineer: KPFF Consulting Engineers
For many, it’s the combination of aesthetics, structural performance, and opportunity for innovation that have proven irresistible. But mass timber also offers a host of other advantages:
Lighter carbon footprint: Mass timber products allow the use of a renewable and sustainable resource as an alternative to more fossil fuel-intensive materials. Designers of ‘tall wood’ buildings have been especially focused on the reduced carbon footprint achieved by using wood, which aligns with the goals of Architecture 2030. Reducing carbon is also a priority for many public buildings and schools.
Construction efficiency: Mass timber construction is fast, and speed correlates to revenue, whether the project is an office, school, student residence, condominium, or hotel. Bernhard Gafner of structural engineering firm Fast + Epp, says that, in his firm’s experience, a mass timber project is approximately 25 percent faster to construct than a similar project in concrete. Noting the advantages for urban infill sites in particular, he says it also offers 90 percent less construction traffic (trucks delivering materials) and requires 75 percent fewer workers on the active deck, making for a much quieter job site.
The fact that mass timber weighs less than other materials also has a number of potential benefits, including smaller foundation requirements and lower forces for seismic resistance. Discussing the new Design Building at the University of Massachusetts, for example, structural engineer Robert Malczyk of Equilibrium Consulting, says, “The seismic force is proportionate to the weight of the building. If this building were designed in concrete, which was considered, the weight would be six times more than the mass timber design.”
Fire and life safety: Structurally, mass timber offers the kind of proven performance—including fire protection and seismic resistance—that allows its use in larger buildings. It also expands the options for exposed wood structure in smaller projects.
Occupant well-being: An increasing number of studies focused on wood’s biophilic aspects have linked the use of exposed wood in buildings with improved occupant health and well-being.1,2
This course is intended for architects and engineers seeking current information on mass timber, including products, research related to structural performance and life safety, and available resources. It answers common questions regarding strength, fire protection, and durability, and highlights examples of mass timber buildings in different occupancy groups to illustrate both design trends and the extent to which mass timber has captured the imagination of North American building designers.
Image courtesy of Fast + Epp
Mass timber systems are a complement to light wood-frame and post-and-beam construction.